Weak acidity of vinyl CH bonds enhanced by halogen substitution
As shown by the rates of proton-deuteron exchange in ethylenes with halogen substituents, the weak acidity of vinyl CH bonds is enhanced by halogen substitution. Relative rates of exchange in basic deuterium oxide reflect the relative acidities. Substitution in the α position has the strongest effect. Less electronegative halogens such as bromine increase the acidity more than does fluorine. The vinyl CH acid strengths correlate closely with the energies of deprotonation of isolated molecules into isolated anions, as computed with the MP2/cc-pVQZ model. The smaller deprotonation energies are associated with the stronger acids. Atomic charges from a natural bond order analysis done with the MP2/aug-cc-pVQZ model show that the negative charge becomes more dispersed in the anions of the stronger acids. Results are given for 13 haloethylenes and for 6 halogen-substituted butadienes, cyclopropenes, and a cyclobutene.
IR spectroscopic study of the dichloromethyl peroxyl radical and its deuterated analogs in the argon matrix
The dichloromethyl peroxyl radical (CHCl2OO?) and its deuterated analog formed in the reaction of the corresponding dichloromethyl radicals with O2 were studied by matrix IR spectroscopy. Dichloromethyl radicals are genera
Baskir, E. G.,Nefedov, O. M.
p. 2236 - 2240
(2022/01/22)
CHLOROACETYLENES AS MICHAEL ACCEPTORS. I. MECHANISM OF ENOLATE DICHLOROVINYLATION.
The condensation of certain enolates with trichloroethylene to yield α-dichlorovinyl ketones has been shown to proceed by way of dichloroacetylene as an obligatory intermediate.
Kende, Andrew S.,Fludzinski, Pawel
p. 2369 - 2372
(2007/10/02)
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